One method of testing fiber optic cable is a visual inspection for continuity. To make sure the fibers are not broken and to trace a fiber from one end to the other, use a visible light fault detector or fiber optic tracer. This tool is like an oversized pen-type flashlight with a light bulb or LED source. It’s very simple to use. Just attach the tracer to the cable and then check the other end of the fiber to see if the light is transmitted. If there’s no light, there’s a bad connection or section of cable. Black Box just introduced two new light sources/fault finders, which you can see at http://www.blackbox.com/go/lightsource.

It’s also a good idea to do a visual fiber inspection on a reel of cable before it’s installed. You can also use tracers to check cable connections in patch panels and with fiber transmitters and receivers.

Some light sources use a red laser light, which is so powerful that you can actually see it through the cable jacket if there are bends and breaks. It’s great for identifying bad connectors and splices.
Black Box offers a number of free resources on fiber optic cable.